Hip abductor force production as a contributor to locomotor cost

The effect of pelvic shape and hip abductor mechanics on locomotor cost has long been debated. However, the contribution of hip abductor force production to overall cost during walking and running has not been established. Recent studies have demonstrated the volume of muscle activated during stance phase is a better predictor of locomotor energetics than other cost determinants. The purpose of this study was to establish the individual contribution of the hip abductors and extensor muscles of the lower limb to locomotor cost. Twenty-six subjects participated in biomechanics testing including force plate and oxygen consumption trials. Anatomical data was determined from full lower body MRIs of each subject. Active muscle volumes in four muscle groups, the hip abductors, hip and knee extensors and ankle plantarflexors, were calculated from joint torques determined by inverse dynamics. Summed active muscle volume (cm3 kg-1 m-1) of the extensor muscle groups explains 86.9% of the variation in mass specific cost (mlO2 kg-1 m-1) during locomotion (P < 0.001). Adding the hip abductors to the model increases explained variance by 1%. This small increase is explained by the high correlation of active muscle volume between each muscle group. However, the hip abductors account for 15% of the total active muscle volume of the lower limb during walking and running suggesting a significant contribution to overall cost. Despite being dimorphic in several measures of the body and pelvis, there were no differences between males and females in mass-specific active muscle volume or locomotor cost at any speed.

This research was funded by: NSF #0850841, The Leakey Foundation, and The Wenner-Gren Foundation